Molecular beam epitaxy (MBE) GaAs grown in the intermediate temperature range of about 400 °C may provide combination of low lifetime, high resistivity, and high mobility. We compare current conduction in unannealed and annealed material grown at 400 °C by fabricating photodetectors on substrates grown between temperature ranges of 250–500 °C. The unannealed version of the device grown at 400 °C shows substantial difference of conduction properties in dark and under light. It is shown that while at low biases the unannealed material may be semi-insulating, at high biases more current is conducted than in annealed material. We attribute this to the effect of intergap states on current conduction and suggest that defect state assisted tunneling is the dominant current transport mechanism in these ranges. Quenching of response by light suggests that occupancy of traps can eliminate their role in current conduction.
Current transport in GaAs grown by molecular beam epitaxy in the intermediate temperature (IT-GaAs) range of about 400 °C is investigated. A model is proposed which explains the direct role of deep defects in assisting tunneling from Schottky contacts to semiconductor, where, due to rapidly changing potential, the Wentzel–Kramers–Brillouin approximation cannot be used. The indirect role of defects in diffusion process in the IT-GaAs semiconductor is also investigated. The model is used to explain the dark I–V behavior of metal–semiconductor–metal photodetectors made on unannealed, i.e., as-grown, IT-GaAs. dc responses of annealed and unannealed IT-GaAs are compared showing much smaller values of dark current in low biases in the unannealed device but sharp increase due to defect assisted tunneling at medium bias levels. Since the defect that best fits the model has an activation energy of about 0.5 eV, the annealing behavior suggests that the As interstitial has all the requisite properties of the defect which determines conduction behavior in this material. The observed reduction of dark response by light at high biases, the negative photoresponse, can then be explained based on occupancy of these defects. Device applications include ohmic contacts based on tunneling through IT-GaAs, and, conversely, reduction of tunneling through growth of a barrier layer between Schottky metal and semiconductor.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.